1. Field of the Invention
The present invention concerns an improved method and apparatus for providing sterile access to fluid lines for fluid sampling. More particularly, the invention relates to an improved method of obtaining precise volumes of substantially undiluted samples of arterial or venous blood for use in blood gas analysis and related therapeutic techniques.
2. Discussion of the Prior Art
Arterial blood pressure measurements have been investigated for more than 250 years. Over the years, the techniques of direct pressure monitoring have been modified and improved so that they now provide clinicians with a valuable tool useful for many purposes, including the direct method of obtaining laboratory specimens of arterial/venous blood from intravenous and/or pressure monitoring lines which are interconnected invasively to the patient.
Within about the last ten years, equipment for direct pressure monitoring has become easier to use, more functional and more readily available. The increased utilization of indwelling arterial/venous catheters has allowed clinicians to take advantage of the easy access to the intra-arterial/venous lines for blood sampling. Accordingly, present practice is to draw substantially all blood specimens from the intra-arterial/venous lines when they are used, thereby decreasing the number of venipunctures required.
Several products and procedures presently exist for use in drawing fluids from arterial/venous monitoring systems. One current method uses an idle side port of a three port stopcock which is protected by a nonvented port protector for sterility and is attached to tubing in a typical pressure monitoring system. Other methods involve the use of a variety of types of commercially available "T-connectors" or "heparin lock" injection/aspiration sites which may be attached at the sideport of a three port stopcock disposed within the most frequently used types of pressure monitoring systems or inline between the arterial/venous catheter and the pressure monitoring line. These prior art sampling systems and procedures as well as the numerous drawbacks thereof will be discussed in greater detail in the paragraphs which follow.